Interim Developer vs Fractional CTO: Which One Your Company Actually Needs
A founder calls us and says "I think we need a CTO." Ten minutes into the conversation it usually turns out they need someone who can ship code this sprint, not someone to run a leadership offsite. The reverse happens too: a company hires a senior contractor to write features, and three months later realizes their actual problem is that nobody owns the technical roadmap. The interim developer vs fractional CTO question comes up constantly, and most companies answer it by guessing.
Both roles are temporary, both are more senior than a typical hire, and both get pitched as a stopgap. That's where the similarity ends. One writes and ships code inside your existing team. The other sets technical direction and rarely touches a keyboard. Picking the wrong one wastes a quarter and doesn't fix the actual gap.
What each role actually does day to day
An interim developer works the way a permanent engineer would. They pick up tickets, review pull requests, push to production, and sit in standups. If your team uses Jira and deploys through a CI pipeline on Fridays, the interim developer uses the same Jira and the same pipeline. We've written about the situations that call for an interim developer in more detail, but the short version is: someone resigned, someone's on leave, or a role sits open during a long search, and the roadmap can't just pause.
A fractional CTO does almost none of that. Their job is judgment: which architecture will hold up at 10x scale, which vendor contract is a mistake, whether the team's testing practices will survive an enterprise security review. Some fractional CTOs do write code occasionally, usually to unblock something the team is stuck on, but that's not the engagement. Our fractional CTO playbook breaks down the four common engagement shapes, from pure advisory to hands-on technical leadership.
The confusion mostly comes from titles. Job boards list "fractional CTO" roles that are really senior interim developer work, and vice versa. Read the actual task list in the posting, not the title.
Weekly hours and how the engagement is structured
An interim developer is usually close to full time. Five days a week, sometimes four, because the point is continuous delivery. You can't ship features with someone who checks in for three hours on Tuesdays. The engagement has a start date, an expected end date tied to a real event (a hire starts, a colleague returns from leave), and a scope that's mostly "keep building what's already planned."
A fractional CTO works in smaller, spread-out chunks: a day a week, two days a month, or an intensive burst around a specific decision like a funding round or a vendor migration. The engagement is open-ended more often than not. Some startups keep a fractional CTO on retainer for a year or longer, because the need (someone senior enough to catch bad decisions before they get expensive) doesn't have a natural end date the way covering parental leave does.
Cost ranges in the European market
Rates vary by seniority, stack, and country, but the ranges are consistent enough to plan around.
An interim developer, senior enough to be productive with minimal ramp-up, typically runs 600 to 1,100 euros per day in Western Europe, depending on the stack and how specialized the work is. A senior Symfony or React developer covering a full-time gap for three months lands somewhere in that band. Because the engagement is close to full time, the monthly cost is comparable to a permanent salary, sometimes a bit higher once you account for the premium on flexibility and speed of onboarding.
A fractional CTO is priced per day too, often 900 to 1,800 euros, but the total monthly spend is usually lower because the hours are fewer. A founder paying for one day a week at 1,200 euros spends around 4,800 euros a month, well under what a full-time CTO salary plus equity would cost. That's the whole appeal of the fractional model: senior judgment without a full-time commitment or a co-founder-level equity grant.
Typical outcomes: what you get when the engagement ends
An interim developer engagement ends with a working codebase and a clean handover. Documentation is current, the permanent hire (or returning colleague) can pick up context in days rather than weeks, and the shipped features match what was on the roadmap when the engagement started. The measurable outcome is delivery: tickets closed, releases shipped, nothing left half-finished.
A fractional CTO engagement ends, or transitions to a lighter retainer, with a different kind of output: an architecture and tech stack the team understands and can extend, a hiring plan for the next senior engineer, a documented set of technical decisions with the reasoning behind them, and usually a stronger internal team than when the engagement started, because part of the job is mentoring whoever will own this after the fractional CTO steps back. The measurable outcome is capability, not a list of shipped tickets.
A short decision checklist
Run through these questions before choosing either path.
Is the immediate problem that code isn't getting written, or that nobody is deciding what code should get written? If tickets are piling up and the team has clear direction but not enough hands, that's an interim developer problem. If the team has capacity but keeps making architectural choices nobody signs off on, that's a fractional CTO problem.
Does the gap have a known end date? A resignation, parental leave, or a search for a permanent hire all have a rough timeline. That points to an interim developer. An ongoing need for senior technical judgment, without a clear point where the need disappears, points to fractional CTO.
Who does the new person report to, and who do they need to convince? An interim developer reports to whoever the engineering lead already is and works inside decisions someone else made. A fractional CTO often needs to influence the founder or the board directly, which requires a different kind of trust and a different kind of contract.
What does your budget actually support? If you can fund something close to a full-time salary for a defined period, an interim developer is realistic. If you can fund a few thousand euros a month indefinitely, a fractional CTO fits better.
Some companies need both, at different points, or even at the same time: a fractional CTO to set the technical direction and an interim developer to actually build against it while a permanent hire is found. That combination is common in fast-growing SaaS teams that outgrew their original setup faster than their hiring pipeline could keep up.
Getting the fit right the first time
Misjudging this costs more than money. Hiring a fractional CTO when you needed someone to write code leaves your backlog exactly where it was, just with a more expensive consultant reviewing it. Hiring an interim developer when you needed technical leadership means the code gets written, but the underlying architectural problem that caused the mess in the first place is still there when they leave.
If you're not sure which side of this you're on, the fastest way to find out is a short conversation about what's actually blocking you this month, not what the org chart says is missing. We work with European companies on both sides of this, sometimes moving from a fractional CTO engagement into an interim developer arrangement as a plan turns into a backlog, or the other way round when an interim developer surfaces a bigger architectural question they weren't scoped to solve.
If you want a second opinion on which fit makes sense for your situation, reach out at hello@wolf-tech.io or find more about how we work.